The present invention pertains to computer systems. More particularly, the invention pertains to virtualization of legacy side-band interfaces in a computer system having a hub interface architecture.
Prior computer systems typically rely on busses such as the Peripheral Component Interconnect (PCI) bus adhering to a Specification Revision 2.1 bus developed by the PCI Special Interest Group of Portland Oreg., to allow computer system chipset components to communicate with one another. For example, a transaction originating at a processor and intended for a disk drive might first be delivered to a first chipset component that serves as an intermediary between the processor bus and a PCI bus. The first chipset component would then deliver the transaction over the PCI bus to a second system chipset component which would then deliver the transaction to the disk drive.
Busses such as the PCI bus also provide for communication with other computer system devices such as graphics controllers and network adapters. Because busses such as the PCI bus must interface with a variety of component types, each with varying requirements, the busses are not necessarily optimized for allowing communication between chipset components. Further, chipset manufacturers who rely on standardized busses such as the PCI bus must adhere to bus standards in order to ensure compatibility with other components, and are not at liberty to make substantial changes in how the chipset components communicate with each other. Another issue that faces chipset component manufacturers in designing and manufacturing chipset components is the need to conform to standardized supply and signaling voltages when relying on busses such as PCI for communication between chipset components, thereby locking the manufacturers into certain design practices and manufacturing technologies.
Yet another problem that confronts chipset component manufactures is the requirement of using direct physical side-band interfaces between the system processor and the chipset in order to support legacy operations from past computer system generations. Such side-band interfaces increase the design complexity of a computer system. In addition, the implementation of direct physical connections requires added cost to the manufacture of chipset components. Therefore, it would be desirable to provide a flexible interface that provides optimal communication between chipset components. Moreover, it would be advantageous to provide a method and mechanism for eliminating the necessity to use physical side band interfaces between chipset components and a system processor.
According to one embodiment, a computer system includes a central processing unit (CPU), a memory control hub (MCH) coupled to the CPU, a point to point interface coupled to the MCH and an input/output control hub (ICH) coupled to the point to point interface. The computer system is adaptable to transmit special cycle signals from the ICH to the CPU via the point to point interface.